Microstructural and magnetic properties on graphitic encapsulated Ni nanocrystals and pure Ni nanoparticles with NiO layer

Two kinds of different nickel nanoparticles with distinct morphological properties, Ni(C) and Ni(O), are studied. Magnetization measurements for the assembly of two kinds os Ni nanoparticles show, a larger coercivity and remanence as well as the deviation between the zero field cooling (ZFC) and the field cooling (FC) magnetization have been observed in the Ni(O) particles. This deviation may be explained as a typical cluster glass-like behavior due to ferromagnetic interaction among the assembly of Ni(O) particles. However, Ni(C) particles exhibit superparamagnetism at room temperature. The average blocking temperature (T_B) is determined to around 115K. We also observe gradual decrease in saturation magnetization, which is attributed to the nanocrystalline nature of the encapsulated particles.